Nuclear fuel , spent components

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

Butex A process for separating the radioactive components of spent nuclear fuel by solvent extraction from nitric acid solution, using diethylene glycol dibutyl ether (also called Butex, or dibutyl carbitol) as the solvent. Developed by the Ministry of Supply (later the UK Atomic Energy Authority) in the late 1940s. Operated at Windscale from 1952 until 1964 when it was superseded by the Purex process. 

SOLVENT extraction (liquid-liquid extraction) is the separation and/or concentration of the components of a solution by distribution between two immiscible liquid phases. A particularly valuable feature is its power to separate mixtures into components according to their chemical type. Solvent extraction is widely used in the chemical industry. Its applications range from hydrometallurgy, e.g., reprocessing of spent nuclear fuel, to fertilizer manufacture and from petrochemicals to pharmaceutical products. Important factors in industrial extraction are the selection of an appropriate solvent and the design of equipment most suited to the process requirements. 

The management of spent nuclear fuel (SNF) for U.S. submarines is intimately intertwined with the overall spent fuel policy of the U.S. This paper summarizes the current SNF policy for the U.S. from both a historical perspective and the perspective of the key issues that are shaping the policy and its future direction. SNF policy focuses on what is known as the backend of the nuclear fuel cycle - all those components of the cycle after the fuel is removed from a reactor. It also can and does impact the front end of the fuel cycle (the components necessary to produce nuclear fuel for a reactor). 

Table 1 Major components in LWR of spent nuclear fuel...

Treatment of Caseous Waste. Gaseous wastes arise from the ventilation of process vessels and the concrete cells that house the plant and equipment used for reprocessing spent nuclear fuel. This gaseous waste is largely air contaminated with small entrained liquid or solid particles containing radioactive components. Some ventilation streams also are contaminated with oxides of nitrogen. 

Nuclear waste is divided into three categories. High-level waste, which is the most radioactive component, forms about 0.2 % of the whole. It is derived mainly from weapons applications and spent nuclear fuel rods. In addition there is about 20% intermediate-level waste, which arises from similar sources and is increased by materials used in reprocessing. This component is not very radioactive and does not liberate large amounts of heat. The remainder, described as low-level waste, is material that is slightly radioactive. Apart from military and nuclear energy sources, this material comes from hospitals, research laboratories and industry, and includes contaminated paper towels, gloves and laboratory equipment. 

The Source Term Working Group was established to prepare a detailed inventory of and release rates for the radionuclides dumped at each Kara Sea disposal site. To this end, inventories were calculated for the spent nuclear fuel (SNF) and activated components at time of disposal and projected forward in time protective barriers, if any, were evaluated for their potential effect on radionuclide release and a number of model scenarios were developed to predict the potential release of the radionuclide inventory into the Kara Sea. 

A thorough state of the art literature review on the corrosion of aluminium alloys was compiled by the IAEA in 1998. This review was published in IAEA-TECDOC-1012, Durability of Spent Nuclear Fuels and Facility Components in Wet Storage. It covered a wide range of quantitative and semi-quantitative data on cladding alloys used in nuclear fuel elements and assemblies, and included separate sections on corrosion of aluminium, zirconium, stainless steel, carbon steels and copper alloys in a wet storage... 

INTERNATIONAL ATOMIC ENERGY AGENCY, Durability of Spent Nuclear Fuels and Facility Components in Wet Storage, IAEA-TECDOC-1012, Vienna (1998). 

The operations and facilities include ore exploration (not included in NFCIS list), mining, ore processing, uranium recovery, chemical conversion to UO2, UO3, UF4, UFg, and uranium metal, isotope enrichment, reconversion of UF to UO2 (after enrichment), and fuel fabrication and assembly that are all part of the front end of the NFC. The central part of the NFC is the production of electric power in the nuclear reactor (fuel irradiation). The back end of the NFC includes facilities to deal with the spent nuclear fuel (SNF) after irradiation in a reactor and the disposal of the spent fuel (SF). The spent fuel first has to be stored for some period to allow decay of the short-lived fission products and activation products and then disposed at waste management facilities without, or after, reprocessing to separate the fission products from the useful actinides (uranium and plutonium). Note the relatively large number of facilities in Table 2.1 dedicated to dealing with the spent fuel. Also listed in Table 2.1 are related industrial activities that do not involve uranium, like heavy water (D2O) production, zirconium alloy manufacturing, and fabrication of fuel assembly components. 

The Interim Spent Fuel Storage Facility (ISFSF) in Jaslovske Bohunice [24,25] is an important component of the spent nuclear fuel management system. The facility has been used for storage purposes since 1987. ISFSF is a nuclear facility that enables the safe storage of the spent nuclear fuel from VVER-440 reactors for a time... 

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